MEMS-based spatial-light modulator with integrated electronics

• US 6,529,311 B1
• Filed: 10/30/2000
• Issued: 03/04/2003
• Est. Priority Date: 10/28/1999
• Status: Active Grant

• Current Assignee: Trustees of Boston University
• Original Assignee: Trustees of Boston University
• Inventors: Horenstein, Mark, Bifano, Thomas
• Primary Examiner(s): Dang, Hung Xuan
• Assistant Examiner(s): TRA, TUYEN Q
• Application Number:
  US09/702,054
• Time in Patent Office: 855 Days
• Field of Search: 359/290, 359/291, 359/223, 359/224, 359/298, 359/248, 359/900
• US Class Current: 359/291
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means

Abstract

Method and apparatus for forming an array of reflective elements for spatial light modulation. The array includes a substrate supporting electronically addressable actuators, each associated with a corresponding reflective element, a coupling attaching each actuator to the corresponding reflective element to place each reflective element in a substantially planar surface. Each electronically addressable actuator responds to predetermined addressing from a processing circuit to reposition the corresponding reflective element out of the planar surface a predetermined distance identified in the predetermined electronic addressing.

Claims

1. A method for fabrication of an array of individually positioned reflectors for spatial light modulation comprising the steps of:

providing plural addressable circuits in an array on a substrate;

forming a flexure supported platform associated with each said circuit, said platform being flexure supported from said substrate; and

attaching a reflecting element to said platform on a side opposite from said substrate thereby providing a plurality of reflecting elements of said array aligned in a surface;

said circuit having electronics operative in response to a signal addressed thereto and operative in association with said platform to apply a force to move said platform and said reflecting element together to a predetermined position out of alignment with the array surface;

wherein said circuits providing step includes the step of providing a conductive plate on said substrate facing said platform, an addressable gate and a voltage memory, said gate operative to apply a voltage in said memory to said plate in response to said signal;

said signal having a voltage component corresponding to the predetermined position to which said reflective element is to be moved and an address component for activating said gate of an appropriately addressed circuit.

2. A method for fabrication of an array of individually positioned reflectors for spatial light modulation comprising the steps of:

providing plural addressable circuits in an array on a substrate;

forming a flexure supported platform associated with each said circuit, said platform being flexure supported from said substrate; and

attaching a reflecting element to said platform on a side opposite from said substrate thereby providing a plurality of reflecting elements of said array aligned in a surface;

said circuit having electronics operative in response to a signal addressed thereto and operative in association with said platform to apply a force to move said platform and said reflecting element together to a predetermined position out of alignment with the array surface;

wherein said circuits providing step includes the step of providing a conductive plate on said substrate patterned as isolated plate electrodes of differing sizes and of providing an address and magnitude decoder responsive to said signal to energize a number of said electrodes corresponding to a decoded magnitude.

3. A method for fabrication of an array of individually positioned reflectors for spatial light modulation comprising the steps of:

providing plural addressable circuits in an array on a substrate;

forming a flexure supported platform associated with each said circuit, said platform being flexure supported from said substrate; and

attaching a reflecting element to said platform on a side opposite from said substrate thereby providing a plurality of reflecting elements of said array aligned in a surface;

said circuit having electronics operative in response to a signal addressed thereto and operative in association with said platform to apply a force to move said platform and said reflecting element together to a predetermined position out of alignment with the array surface;

wherein said forming step includes the steps of;

depositing platform anchors and a metal layer on said substrate using a low temperature process comprising applying and patterning a polymer photoresist; and

forming said platforms using a low temperature process comprising applying and patterning a polymer photoresist and etching said metal layer;

wherein the step of etching a metal layer includes the step of forming flexures in said metal layer connecting said platform to said anchors.

4. A method for fabrication of an array of individually positioned reflectors for spatial light modulation comprising the steps of:

providing plural addressable circuits in an array on a substrate;

forming a flexure supported platform associated with each said circuit, said platform being flexure supported from said substrate; and

attaching a reflecting element to said platform on a side opposite from said substrate thereby providing a plurality of reflecting elements of said array aligned in a surface;

said circuit having electronics operative in response to a signal addressed thereto and operative in association with said platform to apply a force to move said platform and said reflecting element together to a predetermined position out of alignment with the array surface;

wherein said step of attaching a reflecting element includes the steps of;

depositing a metalized layer and strut supporting said metalized layer from said platform using a low temperature process comprising applying and patterning a polymer photoresist and applying and etching a metalized layer.

5. The method of claim 4 further including the step of wet etch releasing any remaining polymer.

6. The method of claim 4 further including the step of planarizing said metalized layer.

7. The method of claim 6 wherein said planarizing step includes one or both of polishing said metalized layer and eroding an outer surface of said metalized layer.

8. The method of claim 6 wherein said planarizing step includes the step of balancing stress vectors within said metalized layer formed during said attaching step.

9. The method of claim 6 wherein said planarizing step includes the step of reactive ion etching of said metalized layer to balance stress vectors within said metalized layer.